Silicone oil is used as a base oil of various compositions in many fields such as cosmetics due to its safety. In particular, in skin care and makeup, silicone oil having a low viscosity of 100 m2/s or less is receiving attention due to its outstanding extensibility, fresh feel and safety, and many companies are considering using it.
However, if low viscosity silicone oil is used as a base oil, for example to prepare a non-flowing pasty composition, the addition amount of thickener must be increased, so a smooth, uniform composition is hard to obtain. Also, since the low viscosity silicone oil easily separates from the composition, there is a problem of low stability.
In order to solve these problems, in the prior art, it was proposed to use organic substances such as dextrin fatty acid ester (Japanese Patent Application Laid-Open (JP-A) Nos. S62-121764, S62-143971, S62-143970, S63-159489), sucrose fatty acid ester (JP-A No. S63-235366), trimethylsilylated polyvinyl alcohol or trimethylsilylated polysaccharides (JP-A No. S62-240335), cellulose ether containing fatty acid ester groups (JP-A No. S63-260955), or inorganic substances such as organic-modified clay minerals (JP-A Nos. S62-45656, S62-54759, S63-72779), as thickeners for low viscosity silicone oil.
However, when these organic or inorganic substances are used as thickeners, there is a problem in that the properties which the low viscosity silicone oil originally had, such as fresh feel and extensibility, decline. A specific silicone polymer was therefore proposed as a thickener, wherein this was treated with a low viscosity silicone oil under a shear force in order to obtain a uniform pasty composition (JP-A No. H02-43263).
In the field of cosmetics, in addition to oils, water is often blended as a required ingredient. In such a case, although a surfactant is used, it is difficult to distribute the silicone oil and water in a homogenous and stable state by conventional methods. The silicone thickener disclosed in JP-A No. H02-43263 also had excellent thickening properties with respect to silicone oil, but it did not give a uniform dispersion when water was blended in. Moreover, some surfactants cause skin irritation, which is undesirable.
In order to resolve this problem, in Japanese Patent (JP-B) No. 2631772 and JP-A No. H05-140320, it is proposed to introduce a polyoxyalkylene group into the molecule of the silicone thickener. The composition disclosed here has the problem that although it has excellent emulsifying properties, the pH falls when the composition is stored for a long time, and the emulsion produced an unpleasant odor.
To resolve this issue, the polyether-modified silicone can be purified by treating it with an acidic aqueous solution (Japanese Patent Application Publication (JP-B) No. H07-91389), or unsaturated groups in the silicone can be hydrogenated (JP-A No. H07-330907). However, these purification techniques are applied to crosslinked polymers, and if they are treated with corrosive acidic aqueous solutions such as aqueous hydrochloric acid, if a glass-lined apparatus is not used, there is a risk that the apparatus will be corroded. Also, even if the unpleasant odor is reduced by this method, the fall of pH due to the characteristic autoxidation of the polyoxyethylene chain cannot be prevented, nor the fall in viscosity and rancid odor due to decomposition of the polyoxyethylene chain. The aforesaid problems can be controlled by addition of antioxidants, but their effect is not sufficient. Moreover, heavy metal catalysts such as palladium and nickel which are used to perform hydrogenation treatment cannot be removed by filtration purification, and since these heavy alloy catalysts remain in the composition, they render it unfit for use in cosmetics.
To resolve the aforesaid problems, the Inventors discovered that:    (1) polymers containing glycerol as a hydrophilic organic group have better solubility and emulsifying properties in various oils than organopolysiloxane polymers having a polyoxyalkylene chain, and    (2) by adding an acidic substance to this glycerol-containing polymer or a pasty composition comprising this polymer and a liquid oil, performing heat treatment, neutralizing with a basic substance and removing the volatile ingredients, a composition with good storage stability free from any unpleasant odor is obtained, and this led to the present invention.
It is therefore a first object of the present invention to provide a hydrophilic polysiloxane polymer having emulsifying properties.
It is therefore a second object of the present invention to provide a pasty composition having emulsifying properties which has very high storage stability and is free from any unpleasant odor.
It is a third object of the present invention to provide a cosmetic material which is free from any unpleasant odor, which is very pleasant to use, and which has excellent long-term stability.